scholarly journals Graphene overcoats for ultra-high storage density magnetic media

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
N. Dwivedi ◽  
A. K. Ott ◽  
K. Sasikumar ◽  
C. Dou ◽  
R. J. Yeo ◽  
...  
Keyword(s):  
Data Storage ◽  
Low Cost ◽  
Hard Disk Drives ◽  
Large Data ◽  
Areal Density ◽  
Limiting Current ◽  
Recording Technology ◽  
Bit Patterned Media ◽  
Fold Reduction ◽  
Carbon Overcoats

AbstractHard disk drives (HDDs) are used as secondary storage in digital electronic devices owing to low cost and large data storage capacity. Due to the exponentially increasing amount of data, there is a need to increase areal storage densities beyond ~1 Tb/in2. This requires the thickness of carbon overcoats (COCs) to be <2 nm. However, friction, wear, corrosion, and thermal stability are critical concerns below 2 nm, limiting current technology, and restricting COC integration with heat assisted magnetic recording technology (HAMR). Here we show that graphene-based overcoats can overcome all these limitations, and achieve two-fold reduction in friction and provide better corrosion and wear resistance than state-of-the-art COCs, while withstanding HAMR conditions. Thus, we expect that graphene overcoats may enable the development of 4–10 Tb/in2 areal density HDDs when employing suitable recording technologies, such as HAMR and HAMR+bit patterned media

scholarly journals Practical Constraint K-Segment Principal Curve Algorithms for Generating Railway GPS Digital Map

2013 ◽  
Vol 2013 ◽  
pp. 1-11
Author(s):  
Dewang Chen ◽  
Long Chen
Keyword(s):  
Data Storage ◽  
Expert Knowledge ◽  
Low Cost ◽  
Large Data ◽  
Gps Data ◽  
Small Data ◽  
Data Sets ◽  
Digital Map ◽  
Digital Maps ◽  
Practical Algorithms

In order to obtain a decent trade-off between the low-cost, low-accuracy Global Positioning System (GPS) receivers and the requirements of high-precision digital maps for modern railways, using the concept of constraint K-segment principal curves (CKPCS) and the expert knowledge on railways, we propose three practical CKPCS generation algorithms with reduced computational complexity, and thereafter more suitable for engineering applications. The three algorithms are named ALLopt, MPMopt, and DCopt, in which ALLopt exploits global optimization and MPMopt and DCopt apply local optimization with different initial solutions. We compare the three practical algorithms according to their performance on average projection error, stability, and the fitness for simple and complex simulated trajectories with noise data. It is found that ALLopt only works well for simple curves and small data sets. The other two algorithms can work better for complex curves and large data sets. Moreover, MPMopt runs faster than DCopt, but DCopt can work better for some curves with cross points. The three algorithms are also applied in generating GPS digital maps for two railway GPS data sets measured in Qinghai-Tibet Railway (QTR). Similar results like the ones in synthetic data are obtained. Because the trajectory of a railway is relatively simple and straight, we conclude that MPMopt works best according to the comprehensive considerations on the speed of computation and the quality of generated CKPCS. MPMopt can be used to obtain some key points to represent a large amount of GPS data. Hence, it can greatly reduce the data storage requirements and increase the positioning speed for real-time digital map applications.

Tunneling Magnetoresistive Heads for Magnetic Data Storage

2007 ◽  
Vol 7 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Sining Mao
Keyword(s):  
Data Storage ◽  
Tunnel Junctions ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Areal Density ◽  
Industrial Applications ◽  
Magnetic Data Storage ◽  
Thermal Dissipation ◽  
Magnetic Data ◽  
Magnetoresistive Heads

Spintronics is emerging to be a new form of nanotechnologies, which utilizes not only the charge but also spin degree of freedom of electrons. Spin-dependent tunneling transport is one of the many kinds of physical phenomena involving spintronics, which has already found industrial applications. In this paper, we first provide a brief review on the basic physics and materials for magnetic tunnel junctions, followed more importantly by a detailed coverage on the application of magnetic tunneling devices in magnetic data storage. The use of tunneling magnetoresistive reading heads has helped to maintain a fast growth of areal density, which is one of the key advantages of hard disk drives as compared to solid-state memories. This review is focused on the first commercial tunneling magnetoresistive heads in the industry at an areal density of 80 ∼ 100 Gbit/in2 for both laptop and desktop Seagate hard disk drive products using longitudinal media. The first generation tunneling magnetoresistive products utilized a bottom stack of tunnel junctions and an abutted hard bias design. The output signal amplitude of these heads was 3 times larger than that of comparable giant magnetoresistive devices, resulting in a 0.6 decade bit error rate gain over the latter. This has enabled high component and drive yields. Due to the improved thermal dissipation of vertical geometry, the tunneling magnetoresistive head runs cooler with a better lifetime performance, and has demonstrated similar electrical-static-discharge robustness as the giant magnetoresistive devices. It has also demonstrated equivalent or better process and wafer yields compared to the latter. The tunneling magnetoresistive heads are proven to be a mature and capable reader technology. Using the same head design in conjunction with perpendicular recording media, an areal density of 274 Gbit/in2 has been demonstrated, and advanced tunneling magnetoresistive heads can reach 311 Gbit/in2. Today, the tunneling magnetoresistive heads have become a mainstream technology for the hard disk industry and will still be a technology of choice for future hard disk products.

PFPE Lubricant Bonding to Carbon Overcoats

2001 ◽  
Author(s):  
Ryan Z. Lei ◽  
Kris R. Paserba ◽  
Andrew J. Gellman ◽  
Nisha Shukla ◽  
Laura M. Cornaglia
Keyword(s):  
Data Storage ◽  
Hard Disk Drives ◽  
Magnetic Data ◽  
Magnetic Media ◽  
Disk Interface ◽  
Pfpe Lubricant ◽  
Carbon Overcoats ◽  
Perfluoropolyalkyl Ether ◽  
Kinetics Of ◽  
Evaporation Kinetics

Abstract Continued reduction in the head-disk spacing of magnetic data storage systems and the resulting increase in the frequency of head-disk contacts will place increasing burdens on the perfluoropolyalkyl ether (PFPE) lubricant and amorphous carbon (a-C) overcoat used to protect the surfaces of magnetic media. In addition, environmental conditions such as temperature, humidity, and contamination that influence the lubricant-overcoat interactions become increasingly important to the tribological performance of the head-disk interface. It is of utmost importance to obtain a fundamental understanding of the molecular interactions at the lubricant-overcoat interface in order to maintain the reliability of future hard disk drives. Recent progress has generated insight into the heterogeneous nature of the a-C overcoat surface, the interaction mechanisms of PFPEs with a-C overcoats, the effects of humidity on lubricant-overcoat interactions, and the evaporation kinetics of PFPE lubricants.

Magnetic Tape: The Challenge of Reaching Hard-Disk-Drive Data Densities on Flexible Media

MRS Bulletin ◽  
2006 ◽  
Vol 31 (5) ◽  
pp. 404-408 ◽  
Author(s):  
Richard H. Dee
Keyword(s):  
Data Storage ◽  
Magnetic Tape ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Areal Density ◽  
Operating Conditions ◽  
Magnetic Data ◽  
Disk Drives ◽  
Placement Problem ◽  
The Future

AbstractBy the end of 2006, the areal density of magnetic recording on tape will approach that seen in hard disk drives of the early to mid-1990s.These operating conditions are reviewed in relation to the operating conditions deemed necessary for the future of magnetic data storage on tape.What results is a clear set of tasks, encompassing both materials and systems architecture issues, to achieve very high-density data storage on magnetic tape, leading to 10 Tbyte tape cartridge capacities and higher.The key to achieving on tape the areal densities of tens to hundreds of Gbit in.2, common in hard disk drives (HDDs), lies primarily in the properties of the medium itself.As for volumetric density of the storage entity, HDDs and tape cartridges are roughly equivalent.The mechanical dimensional uncertainties that accompany the use of flexible, as opposed to rigid, media means that both the mechanical and magnetic properties of materials play a key role in the future of tape.The need for new architectures to overcome the track placement problem that results from increasing track density on flexible media are reviewed, as well as the “particles in a binder” concept that has served so well as the physical basis of tape media over the past 50 years.

scholarly journals Design and Micromagnetic Simulation of Fe/L10-FePt/Fe Trilayer for Exchange Coupled Composite Bit Patterned Media at Ultrahigh Areal Density

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Warunee Tipcharoen ◽  
Arkom Kaewrawang ◽  
Apirat Siritaratiwat
Keyword(s):  
Exchange Coupling ◽  
Single Layer ◽  
Areal Density ◽  
Interlayer Exchange Coupling ◽  
Magnetic Media ◽  
Recording Technology ◽  
Bit Patterned Media ◽  
Patterned Media ◽  
Interlayer Exchange ◽  
Exchange Coupled Composite

Exchange coupled composite bit patterned media (ECC-BPM) are one candidate to solve the trilemma issues, overcome superparamagnetic limitations, and obtain ultrahigh areal density. In this work, the ECC continuous media and ECC-BPM of Fe/L10-FePt/Fe trilayer schemes are proposed and investigated based on the Landau-Lifshitz-Gilbert equation. The switching field,Hsw, of the hard phase in the proposed continuous ECC trilayer media structure is reduced below the maximum write head field at interlayer exchange coupling between hard and soft phases,Aex, higher than 20 pJ/m and its value is lower than that for continuousL10-FePt single layer media andL10-FePt/Fe bilayer. Furthermore, theHswof the proposed ECC-BPM is lower than the maximum write head field with exchange coupling coefficient between neighboring dots of 5 pJ/m andAexover 10 pJ/m. Therefore, the proposed ECC-BPM trilayer has the highest potential and is suitable for ultrahigh areal density magnetic recording technology at ultrahigh areal density. The results of this work may be gainful idea for nanopatterning in magnetic media nanotechnology.

scholarly journals The Head-Disk Interface Roadmap to an Areal Density of Tbit/in2

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Bruno Marchon ◽  
Thomas Pitchford ◽  
Yiao-Tee Hsia ◽  
Sunita Gangopadhyay
Keyword(s):  
Hard Disk Drives ◽  
Rotating Disk ◽  
Areal Density ◽  
Disk Surface ◽  
Inert Atmosphere ◽  
Annual Growth Rate ◽  
Head Disk Interface ◽  
Bit Patterned Media ◽  
Disk Interface ◽  
Compound Annual Growth Rate

This paper reviews the state of the head-disk interface (HDI) technology, and more particularly the head-medium spacing (HMS), for today’s and future hard-disk drives. Current storage areal density on a disk surface is fast approaching the one terabit per square inch mark, although the compound annual growth rate has reduced considerably from ~100%/annum in the late 1990s to 20–30% today. This rate is now lower than the historical, Moore’s law equivalent of ~40%/annum. A necessary enabler to a high areal density is the HMS, or the distance from the bottom of the read sensor on the flying head to the top of the magnetic medium on the rotating disk. This paper describes the various components of the HMS and various scenarios and challenges on how to achieve a goal of 4.0–4.5 nm for the 4 Tbit/in2density point. Special considerations will also be given to the implication of disruptive technologies such as sealing the drive in an inert atmosphere and novel recording schemes such as bit patterned media and heat assisted magnetic recording.

scholarly journals Soft-Output Detector Using Multi-Layer Perceptron for Bit-Patterned Media Recording

2022 ◽  
Vol 12 (2) ◽  
pp. 620
Author(s):  
Seongkwon Jeong ◽  
Jaejin Lee
Keyword(s):  
Data Storage ◽  
Probability Distributions ◽  
Storage System ◽  
Areal Density ◽  
Magnetic Data ◽  
Multi Layer Perceptron ◽  
Bit Patterned Media ◽  
Patterned Media ◽  
Ber Performance ◽  
Conventional Detection

As conventional data storage systems are faced with critical problems such as the superparamagnetic limit, bit-patterned media recording (BPMR) has received significant attention as a promising next-generation magnetic data storage system. However, the reduced spacing between islands at increased areal density causes severe intersymbol and intertrack interference, which degrade BPMR system performance. In this study, we introduce a soft-output detector using multi-layer perceptron to predict reliable information. A received signal is equalized and detected by the MLP detector. The MLP detector provides a well-estimated value by using the binary-cross entropy function as a loss function and the identity function as an activation function for the output layer of the MLP detector. This study investigates the received probability distributions out of the detectors and compares the performance of various versions against a conventional detector. Compared with the conventional detection, the proposed MLP detectors provide a small variance and better BER performance than the conventional detection. Simulations of MLP designs show an advantage over conventional detection. Moreover, the proposed MLP detectors with the demodulator exhibit better BER performance than the conventional detector with the demodulator.

A Facile Approach of Fabricating Ultra-Thin Wear Resistant Si/SiNx/C Overcoats for Magnetic Tape Recording Heads

2014 ◽  
Author(s):  
Reuben J. Yeo ◽  
Neeraj Dwivedi ◽  
Christina Y. H. Lim ◽  
C. S. Bhatia
Keyword(s):  
Data Storage ◽  
Magnetic Tape ◽  
Low Cost ◽  
Physical Contact ◽  
Tape Recording ◽  
Recording Technology ◽  
Magnetic Spacing ◽  
Head Surface ◽  
Magnetic Tape Recording ◽  
Tape Medium

Magnetic tape recording is one of the oldest data storage technologies, and it is still used today due to its low cost and long data storage life. Magnetic tape recording is a contact recording technology, where a thin flexible magnetic tape medium is pulled across an Al2O3/TiC (AlTiC) recording head surface at a high velocity while in direct physical contact with each other. As a result, one of the inherent problems faced in magnetic tape recording systems is an increase in the magnetic spacing over time with prolonged usage, due to continuous wear of the tape bearing head surface, which in turn leads to a deterioration of the magnetic readback signal [1]. The increase in the magnetic spacing at the head-tape interface can be due to several factors, such as pole tip recession (PTR), accumulation of wear debris on the head and surface roughness of the head and tape medium. Out of these factors, PTR is a major contributor to the magnetic spacing loss, due to a higher rate of wear of the softer magnetic read and write poles at the head-tape interface [2].

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